Scroll compressor

ABSTRACT

A scroll compressor having an improved compression efficiency by optimizing a step mesh gap in an operating state is provided. The scroll compressor having a step-like shape has a step-mesh-gap set value occurring between step side surfaces of a connecting wall of a fixed scroll and a connecting edge of a revolving scroll and a step-mesh-gap set value occurring between step side surfaces of a connecting wall of the revolving scroll and a connecting edge of the fixed scroll, and a fixed-side set value for when the two move close together due to the revolving scroll tilting by receiving gas pressure during operation is set greater than that for when the two move apart.

TECHNICAL FIELD

The present invention relates to scroll compressors applied to, forexample, air conditioners and refrigerators.

BACKGROUND ART

In a scroll compressor, spiral walls of a fixed scroll and a revolvingscroll are interlocked, and the revolving scroll orbitally revolvesaround the fixed scroll so as to gradually reduce the volume of acompression chamber formed between the walls to compress a fluid insidethe compression chamber. In such scroll compressors, since it ispossible to improve the compression ability by increasing thecompression ratio without increasing the size of the compressor itself,a scroll compressor with a scroll member having a step-like shape is putto actual use (for example, refer to Patent Document 1.

Patent Document 1: Japanese Unexamined Patent Application, PublicationNo. 2003-35285

DISCLOSURE OF INVENTION

In order to permit revolution of the revolving scroll at theabove-described stepped section of the scroll member, a minute gap isformed between the fixed scroll and the revolving scroll. Consequently,as the volume of the compression chamber gradually decreases as thecompression process proceeds, compression gas leaks through the minutegap from the high-pressure side to the low-pressure side. Therefore, theminute gap formed at the stepped section causes a reduction in thecompression efficiency of the scroll compressor.

A gap known as a “step mesh gap” is provided at the stepped section of ascroll compressor employing a step-like shape to serve as such a minutegap that acts as a leakage path of the compression gas. The step meshgaps are gaps formed between the stepped sections (between theconnecting edge and the connecting wall) of the bottom side and the tipside of the stepped section having a step-like shape. The two step meshgaps in the scroll compressor are set to be equal when the operation isstopped.

However, with the above-described step mesh gaps, when the scrollcompressor is operated and the revolving scroll starts the compressionoperation, one of the step mesh gaps becomes small due to the tilting ofthe revolving scroll, whereas the other becomes large due to separation.From such a viewpoint, there is a need for improving the efficiency byoptimizing the step mesh gaps during operation of the scroll compressorand reducing the leakage amount of compressed gas that leaks from thehigh-pressure side to the low-pressure side through the step mesh gapsduring operation.

The present invention has been conceived in light of the problemsdescribed above, and it is an object thereof to provide a scrollcompressor having an improved compression efficiency by optimizing stepmesh gaps in an operating state.

To solve the problems described above, the present invention providesthe following solutions.

A scroll compressor according to the present invention includes a fixedscroll having a spiral wall vertically provided on one side surface ofan end plate, and a revolving scroll having spiral wall verticallyprovided on one side surface of an end plate and being supported in sucha manner as to be capable of orbitally revolving while rotation isprevented by meshing the walls, wherein a stepped section is formed onthe side surface of at least one of the end plates of the fixed scrolland the revolving scroll such that the height along the spiral of thewalls is high at the center portion and low at the outward end, andwherein an upper edge of the other wall of the fixed scroll or therevolving scroll, corresponding to the stepped section of the end plateis divided into a plurality of sections, and has a step-like shape suchthat the height of the sections is low at the center portion of thespiral and high at the outward end, wherein the scroll compressor has afirst step-mesh-gap set value (Hf) occurring between step side surfacesat a bottom of the fixed scroll and a tip of the revolving scroll and asecond step-mesh-gap set value (H0) occurring between a bottom of therevolving scroll and a tip of the fixed scroll, and a fixed-side setvalue for when the two move close together due to the revolving scrolltilting by receiving gas pressure during operation is set greater thanthat for when the two move apart.

With the scroll compressor according of the present invention, a firststep-mesh-gap set value (Hf) occurring between step side surfaces at abottom of the fixed scroll and a tip of the revolving scroll and asecond step-mesh-gap set value (H0) occurring between a bottom of therevolving scroll and a tip of the fixed scroll are set such that afixed-side set value for when the two move close together due to therevolving scroll tilting by receiving gas pressure during operation isset greater than that for when the two move apart; therefore, when therevolving scroll tilts by receiving gas pressure during operation, thestep mesh gap when moving close together and the step mesh gap whenmoving away from each other can be set to substantially minimum optimalvalues, and thus the leakage amount from the step mesh gaps can bereduced.

It is preferable that the first and second step-mesh-gap set values (Hfand H0) be set such that a step mesh gap amount (he) formed at the endof the meshing is smaller than a step mesh gap amount (hs) formed at thebeginning of the meshing (hs>he), and a step mesh gap amount (h)gradually decrease from the start of the meshing to the end of themeshing. In this way, the step mesh gap amount (h) decreases as thepressure difference becomes large. Thus, the leakage amount from thestep mesh gaps can be reduced.

It is preferable that cross-sectional shapes of a bottom and a tipmeshing at the stepped section be asymmetrical, with the radii ofcurvature varied such that the contact area increases from a meshingstart time to a meshing end time. In this way, the sealing abilityincreases by increasing the contact area when the pressure difference islarge. Thus, the leakage amount from the step mesh gaps can be reduced.

According to the above-described present invention, the step mesh gapformed between the side surfaces of the bottom side and the tip side atthe stepped section having a step-like shape is optimized in theoperation state, and the amount of compressed gas leaking from the gapstep mesh gap during the compression process during operation can bereduced; therefore, a significant advantage is achieved in that thecompression efficiency of the scroll compressor increases.

Moreover, by setting the step mesh gap small in the last half of thecompression process when the pressure difference is large and byincreasing the sealing ability by employing an asymmetricalcross-section in which the contact area of the connecting wall and theconnecting edge increase in the last half of the compression processwhen the pressure difference is large, the compression efficiency of thescroll compressor having a stepped section with a step-like shape can beimproved even more.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1A is a plan view of an embodiment of a scroll compressor accordingto the present invention in a meshing state of a fixed scroll and arevolving scroll when operation is stopped.

FIG. 1B is an enlarged view of a stepped section 42 and its periphery inFIG. 1A.

FIG. 1C is an enlarged view of a stepped section 43 and its periphery inFIG. 1A.

FIG. 2A is a plan view of an embodiment of a scroll compressor accordingto the present invention in a meshing state of a fixed scroll and arevolving scroll when operation is stopped.

FIG. 2B is an enlarged view of a stepped section 42 and its periphery inFIG. 2A.

FIG. 2C is an enlarged view of a stepped section 43 and its periphery inFIG. 2A.

FIG. 3 is a partial sectional view of an example configuration of ascroll compressor according to the present invention.

FIG. 4A is a perspective view of an example configuration of a scrollcompressor according to the present invention with a fixed scrollvertically inverted.

FIG. 4B is a perspective view of an example configuration of a revolvingscroll of a scroll compressor according to the present invention.

FIG. 5 is a sectional view of a state at the beginning of compressionwhere a compression chamber is formed by interlocking a fixed scroll anda revolving scroll.

FIG. 6 is an enlarged partial view of the stepped section according tothe present invention, illustrating each stage of the compressionoperation in which compression is started at the beginning of meshingshown in (a) and is ended in (e).

FIG. 7 is an enlarged partial view of the stepped section according to amodification of the present invention, illustrating each stage of thecompression operation in which compression is started at the beginningof meshing shown in (a) and is ended in (e).

EXPLANATION OF REFERENCE SIGNS

-   1: housing-   2: discharge cover-   11: discharge port-   12: fixed scroll-   12 a, 13 a: end plate-   12 b, 13 b: wall-   12 c, 12 d, 13 c, 13 d: upper edge (tip)-   12 e, 13 e: connecting edge (tip)-   12 f, 12 g, 13 f, 13 g: bottom surface (bottom)-   12 h, 13 h: connecting wall (bottom)-   13: revolving scroll-   42, 43: stepped section-   C: compression chamber-   Hf, H0: step-mesh-gap set value-   h, hs, he: step mesh gap amount

BEST MODE FOR CARRYING OUT THE INVENTION

An embodiment of a scroll compressor according to the present inventionwill be described below with reference to the drawings.

FIG. 3 is a sectional view of an example configuration of a scrollcompressor. In the drawing, reference numeral 1 represents a sealedhousing, reference numeral 2 represents a discharge cover thatpartitions the interior of the housing 1 into a high-pressure chamber HRand a low-pressure chamber LR, reference numeral 5 represents a frame,reference numeral 6 represents an intake pipe, reference numeral 7represents a discharge pipe, reference numeral 8 represents a motor,reference numeral 9 represents a rotary shaft, and reference numeral 10represents a rotation prevention mechanism. Moreover, reference numeral12 represents a fixed scroll, and reference numeral 13 represents arevolving scroll meshed with the fixed scroll 12.

As shown in FIG. 4, the fixed scroll 12 is constructed by verticallymounting a spiral wall 12 b on one side of an end plate 12 a. As shownin FIG. 4B, the revolving scroll 13 is constructed, in the same manneras the fixed scroll 12, by vertically mounting a spiral wall 13 b on oneside of an end plate 13 a. In particular, the wall 13 b hassubstantially the same shape as the wall 12 b of the fixed scroll 12.The revolving scroll 13 and the fixed scroll 12 are decentered relativeto each other by a radius of revolution with their phases shifted by180° and are installed by meshing the walls 12 b and 13 b with eachother.

In such a case, the revolving scroll 13 revolves around the fixed scroll12 by the operation of the rotation prevention mechanism 10 and arevolving eccentric pin 9 a that is provided at the upper edge of therotary shaft 9 driven by the motor 8. The fixed scroll 12 is fixed tothe housing 1 and is provided with a discharge port 11 for compressedfluid disposed at the center of the rear side of the end plate 12 a.

A stepped section 42, formed such that the height in the spiraldirection at the center portion of the wall 12 b is high and the heightat the outward end is low, is provided on one side of the end plate 12 aof the fixed scroll 12, where the wall 12 b is vertically provided.Similar to the end plate 12 a of the fixed scroll 12, the end plate 13 aof the revolving scroll 13, where the wall 13 b is vertically provided,is provided with a stepped section 43, formed such that the height inthe spiral direction at the center portion of the wall 13 b is high andthe height at the outward end is low. The stepped sections 42 and 43 areprovided at positions shifted by π (rad) from the outward ends (intakeside) to the inward ends (discharge side) of the walls 12 b and 13 b.

The bottom surface of the end plate 12 a is divided into two sections bythe stepped section 42: a shallow bottom surface 12 f adjoining thecenter portion and a deep bottom surface 12 g adjoining the outer end.The adjacent bottom surfaces 12 f and 12 g constitute the steppedsection 42, and a connecting wall 12 h connecting the bottom surfaces 12f and 12 g is vertically provided.

Similar to the above-described end plate 12 a, the end plate 13 a isdivided into two sections by the stepped section 43: a shallow bottomsurface 13 f adjoining the center portion and a deep bottom surface 13 gadjoining the outer end. The adjacent bottom surfaces 13 f and 13 gconstitute the stepped section 43, and a connecting wall 13 h connectingthe bottom surfaces 13 f and 13 g is vertically provided.

The wall 12 b of the fixed scroll 12 corresponds to the stepped section43 of the revolving scroll 13, and the spiral upper edge thereof isdivided into two sections and has a step-like shape in which the heightof the center portion is high and the height of the outer end is low.Similar to the wall 12 b, the wall 13 b of the revolving scroll 13corresponds to the stepped section 42 of the fixed scroll 12, and thespiral upper edge thereof is divided into two sections and has astep-like shape in which the height of the center portion is high andthe height of the outer end is low.

More specifically, the upper edge of the wall 12 b is separated into twosections: a low upper edge 12 c provided closer to the center portionand a high upper edge 12 d provided closer to the outward end. Avertical connecting edge 12 e connecting the adjacent upper edges 12 cand 12 d is provided therebetween. Similar to the above-described wall12 b, the upper edge of the wall 13 b is separated into two sections: alow upper edge 13 c provided closer to the center portion and a highupper edge 13 d provided closer to the outward end. A verticalconnecting edge 13 e connecting the adjacent upper edges 13 c and 13 dis provided therebetween.

The connecting edge 12 e smoothly continues to the outer and inner sidesof the wall 12 b when viewed from the revolving scroll 13 direction ofthe wall 12 b and forms a semicircle having a diameter equal to thethickness of the wall 12 b. Similar to the connecting edge 12 e, theconnecting edge 13 e smoothly continues to the outer and inner sides ofthe wall 13 b and forms a semicircle having a diameter equal to thethickness of the wall 13 b.

When viewed from the revolving axis direction of the end plate 12 a, theconnecting wall 12 h forms an arc that aligns with the envelope curveformed by the connecting edge 13 e while the revolving scroll revolves.Similar to the connecting wall 12 h, the connecting wall 13 h alignswith the envelope curve formed by the connecting edge 12 e.

On the wall 12 b of the fixed scroll 12, tip seals 14 a and 14 b, whichare divided into two near the connecting edge 12 e, are provided at theupper edges 12 c and 12 d. Similarly, on the wall 13 b of the revolvingscroll 13, tip seals 15 a and 15 b, which are divided into two near theconnecting edge 13 e, are provided at the upper edges 13 c and 13 d. Thetip seals seal tip-seal gaps formed between the upper edge (tip) and thebottom surface (bottom) between the revolving scroll 12 and the fixedscroll 13 and minimize compressed gas/fluid leakage.

Specifically, when the revolving scroll 13 is meshed with the fixedscroll 12, the tip seal 15 b provided at the low upper edge 13 ccontacts the shallow bottom surface 12 f, and the tip seal 15 a providedat the high upper edge 13 d contacts the deep bottom surface 12 g. Atthe same time, the tip seal 14 a provided at the low upper edge 12 ccontacts the shallow bottom surface 13 f, and the tip seal 14 b providedat the high upper edge 12 d contacts the deep bottom surface 13 g. As aresult, compression chambers C are formed between the scrolls 12 and 13and are partitioned by the end plates 12 a and 13 a and the walls 12 band 13 b facing each other. In FIG. 4A, the top and bottom of the fixedscroll 12 are inverted so as to show the step-like shape of the fixedscroll 12.

FIG. 5 illustrates the compression chambers C, formed by interlockingthe fixed scroll 12 and the revolving scroll 13 a, in a compressionstart state. In this compression start state, the outward end of thewall 12 b contacts the outer surface of the wall 13 b, the outward endof the wall 13 b contacts the outer surface of the wall 12 b, fluid tobe compressed is sealed between the end plates 12 a and 13 a and thewalls 12 b and 13 b, and two compression chambers C having maximumvolume are formed at positions facing each other on either side of thecenter of the scroll compressor mechanism. At this point, the connectingedge 12 e and the connecting wall 13 h, and the connecting edge 13 e andthe connecting wall 12 h are sliding against each other. However, theyare moved apart immediately after the revolving operation of the fixedscroll 12.

When the above-described fixed scroll 12 and revolving scroll 13 are inan interlocked state, step-mesh-gap set values H0 and Hf (see FIGS. 1Band 1C) at the two stepped sections 42 and 43 set as described belowwhen operation is stopped with no load applied. The step mesh gaps aregaps formed in the stepped sections 42 and 43, between connecting edges12 e and 13 e, which are step side surfaces on the tip sides, and theconnecting walls 12 h and 13 h, which are side surfaces of the stepsections on the bottom sides.

Specifically, when a first step-mesh-gap set value (hereinafter referredto as “fixed-side set value”) Hf generated between the step sidesurfaces of the connecting wall (tip-side step wall) 12 h of the fixedscroll 12 and the connecting edge (bottom-side step wall) of therevolving scroll 13 at the stepped section 42 is compared with a secondstep-mesh-gap set value (hereinafter referred to as “revolving-side setvalue”) H0 generated between the step side surfaces of the connectingwall 13 h (step wall on bottom side) of the revolving scroll 13 and theconnecting edge (step wall on tip side) 12 e of the fixed scroll 12 atthe stepped section 43, the fixed-side set value Hf for when the twomove close together due to the revolving scroll 13 tilting by receivinggas pressure during operation is set greater than the revolving-side setvalue H0 for when the two move apart (Hf>H0).

When the above-described scroll compressor starts operation, therevolving scroll 13 slightly tilts to the right in the plane of thedrawing (clockwise) by receiving gas pressure, as shown in FIGS. 2A to2C. Therefore, the fixed-side set value Hf and the revolving-side setvalue H0 set during the stopped state shown in FIGS. 1A to 1C change toa fixed-side step mesh value Hf′ and a revolving side step mesh valueH0′ due to the tilting of the revolving scroll 13.

Since the connecting edge 13 e moves close to the connecting wall 12 hdue to the tilting of the revolving scroll 13, the fixed side step meshvalue Hf′ becomes smaller than the fixed-side set value Hf set in thestopped state. On the other hand, since the connecting edge 12 e movesaway from the connecting wall 13 h due to the tilting of the revolvingscroll 13, the revolving-side step mesh value H0′ becomes greater thanthe revolving-side set value H0 set in the stopped state.

Therefore, for the step mesh gap in the stopped state with the revolvingscroll 13 tilted, the fixed side step mesh value Hf′ on the steppedsection 42 side is smaller than that of a stopped state and therevolving side step mesh value H0′ on the stepped section 43 side aftermoving away is smaller than usual; therefore, the revolving side and thefixed side are optimized and the overall opening area can be reduced.Consequently, the gas volume leaking from the high-pressure side to thelow-pressure side through the opening area of the step mesh gap in thecompression process of the scroll compressor is reduced; thus, thecompression efficiency of the scroll compressor employing a step-likeshape can be improved.

At the stepped sections 42 and 43 of the scroll compressor, thefixed-side set value Hf and the revolving-side set value H0 are set suchthat a step mesh gap amount he formed at the end of the meshing issmaller than a step mesh gap amount hs formed at the beginning of themeshing of the fixed scroll 12 and the revolving scroll 13 (hs>he), anda step mesh gap amount h gradually decreases from the start of themeshing to the end of the meshing, as shown in FIG. 6.

In such a case, the cross-sections of the connecting walls (bottoms) 12h and 13 h and the connecting edges (tips) 12 e and 13 e meshing at thestepped sections 42 and 43 are substantially semicircular.

In FIG. 6, compression starts from the meshing start state illustratedin (a), proceeds through (b) to (d) as the compression process of theconnecting edge 13 e of the revolving scroll 13 proceeds, and ends in(e). In such a compression process, the compression chamber C is dividedinto a high-pressure side PH and a low-pressure PL by the wall 13 b ofthe revolving scroll 13.

However, at the beginning of compression when the pressure difference ofthe high-pressure side PH and the low-pressure side PL is small, theleakage amount of compressed gas is not very large even when the stepmesh gap amount h is relatively large. Then, as the compression processproceeds and the pressure difference between the high-pressure side PHand the low-pressure side PL increases, the leakage amount increases ifthe step mesh gap amount h is constant. However, since the step mesh gapamount h is set such that it gradually decreases, the leakage amount ofcompressed gas is restricted to a small amount. As a result, since theleakage amount of compressed gas through the overall compression processcan be reduced, the compression efficiency of the scroll compressoremploying a step-like shape can be improved.

FIG. 7 illustrates a modification of the above-described FIG. 6; thecross-sections of connecting walls (bottoms) 12 h′ and 13 h′ andconnecting edges (tips) 12 e′ and 13 e′ meshing at stepped sections 42′and 43′ are asymmetrical with different radii of curvature such that thecontact area increases from the meshing start time to the meshing endtime.

In FIG. 7, compression starts from the meshing start state illustratedin (a), proceeds through (b) to (d) as the compression process of theconnecting edge 13 e′ of the revolving scroll 13 proceeds, and ends in(e). In such a compression process, the compression chamber C is dividedinto a high-pressure side PH and a low-pressure PL by the wall 13 b ofthe revolving scroll 13.

In this modification, since the radii of curvature are asymmetrical, thesealing ability is increased by increasing the contact area of theconnecting walls and connecting edges when the pressure differencebetween the high-pressure side PH and the low-pressure side LH is large.

Specifically, in the meshing start state, since the pressure differenceis small, the leakage amount is not very large even when the contactarea is reduced to line contact. However, the cross-sections, havingasymmetrical radii of curvature, of the connecting walls (bottoms) 12 h′and 13 h′ and the connecting edges (tips) 12 e′ and 13 e′ are shapedsuch that the contact changes from line contact to surface contact asthe compression process proceeds and the pressure difference increases;therefore, a sufficient sealing ability is achieved since the contactarea increases in the last half of the compression process when thepressure difference is large. Consequently, the leakage amount from thestep mesh gap is reduced in the last half of the compression processeven when the pressure difference is large, and therefore, thecompression efficiency of the scroll compressor employing a step-likeshape can be improved.

In this way, with the scroll compressor according to the presentinvention, the step mesh gap formed between the side surfaces on thebottom side and the tip side of the stepped sections 42 and 43 havingstep-like shapes is optimized such that it becomes small in an operatingstate. As a result, the amount of compressed gas leakage from the gapstep mesh gap in the compression process during operation can bereduced. Therefore, a significant advantage is achieved in that thecompression efficiency of the scroll compressor having a stepped sectionwith a step-like shape is improved.

The step mesh gap becomes smaller toward the last half of thecompression process when the pressure difference is large. For thisreason also, a significant advantage is achieved in that the compressionefficiency of the scroll compressor having a stepped section with astep-like shape is improved. An asymmetrical cross-section thatincreases the contact area of the connecting wall and the connectingedge when the pressure difference is large is employed and the sealingability is increased in the last half of the compression process. Forthis reason also, a significant advantage is achieved in that thecompression efficiency of the scroll compressor having a stepped sectionwith a step-like shape is improved.

The present invention is not limited to the embodiments described above,and various modifications may be made so long as they do not depart fromthe spirit of the invention.

1. A scroll compressor comprising a fixed scroll having a spiral wallvertically provided on one side surface of an end plate, and a revolvingscroll having spiral wall vertically provided on one side surface of anend plate and being supported in such a manner as to be capable oforbitally revolving while rotation is prevented by meshing the walls,wherein a stepped section is formed on the side surface of at least oneof the end plates of the fixed scroll and the revolving scroll such thatthe height along the spiral of the walls is high at the center portionand low at the outward end, and wherein an upper edge of the other wallof the fixed scroll or the revolving scroll, corresponding to thestepped section of the end plate is divided into a plurality ofsections, and has a step-like shape such that the height of the sectionsis low at the center portion of the spiral and high at the outward end,wherein the scroll compressor has a first step-mesh-gap set value (Hf)occurring between step side surfaces at a bottom of the fixed scroll anda tip of the revolving scroll and a second step-mesh-gap set value (H0)occurring between step side surfaces at a bottom of the revolving scrolland a tip of the fixed scroll, and a fixed-side set value for when thetwo move close together due to the revolving scroll tilting by receivinggas pressure during operation is set greater than that for when the twomove apart.
 2. The scroll compressor according to claim 1, wherein thefirst and second step-mesh-gap set values (Hf and H0) are set such thata step mesh gap amount (he) formed at the end of the meshing is smallerthan a step mesh gap amount (hs) formed at the beginning of the meshing(hs>he), and a step mesh gap amount (h) gradually decreases from thestart of the meshing to the end of the meshing.
 3. The scroll compressoraccording to claim 1, wherein cross-sectional shapes of a bottom and atip meshing at the stepped section are asymmetrical, with the radii ofcurvature varied such that the contact area increases from a meshingstart time to a meshing end time.